The present invention relates to a servo system for controlling a plurality of movable objects such that the objects travel timed to each other. The drive source for each of the object may be, but not limited to, a servo motor.
In a prior art servo system employed for the purpose described above, a time lag between two movable objects, for example, is compensated for by delaying the generation of a drive start signal for one of them by a predetermined period of time with respect to the generation of a drive start signal for the other.
In detail, where a control is performed such that at a time To when one b of the movable objects has run to reach a position xb, the other movable object a has also reached a position xa, the following equations hold: ##EQU1## where .alpha.a and .alpha.b are accelerations acting on the objects a and b at a start or buildup of movement thereof, and Vfa and Vfb are target velocities for the constant velocity runs of the respective objects.
Therefore, the delay time T.sub.D is expressed as: EQU T.sub.D =To-TRa (3)
The prerequisite to be pointed out here is that the accelerations .alpha.a and .alpha.b be so selected as to set up a relation TRa.ltoreq.To and insure a time margin up to the time To, which is produced by: ##EQU2##
A problem encountered with the prior art system discussed above is that the accelerations .alpha.a and .alpha.b in the equations are susceptive to the characteristics of servo motors, frictions developing during the movement of the objects, ambient temperature, changes with the lapse of times, as well as other various factors.